1. Field of the invention
The present invention relates to an endoscope and, more specifically, to an endoscope featured by a curving mechanism for curving a curving portion.
2. Description of the Related Art
In a non-destructive inspection of compressor blades (hereinafter referred to as "blades") inside a jet engine by means of an industrial endoscope, there may be found damage such as a nick or a crack in a blade edge as caused by sucking of a bird, a stone, a piece of ice, or the like during operation of the jet engine.
In such a case, even if a damaged portion is small, if the jet engine is used without repairing it, stress may be concentrated on the damaged portion, possibly enlarging the damaged portion. When a damaged blade becomes not suitable for use, a common procedure is to disassemble and repair the jet engine. The damaged blade is removed from the engine, and is repaired by grinding into such a shape that there occurs no stress concentration on the damaged portion or replaced by a new one. However, the procedure of disassembling an engine and performing a grinding operation every time a small damaged portion is found has a problem that the repairing takes undue cost and time.
In general, a jet engine has, approximately for each blade, a hole (hereinafter referred to as "access port") for inspection of the blade. Various industrial endoscope apparatuses have been proposed that can repair, by grinding, a damaged portion of a blade edge to avoid stress concentration during operation without disassembling the engine such that a processing device mounted with a rotary processing member at its tip is inserted, together with an industrial endoscope, into the inside of the engine through the access port, then the rotary processing member located at the tip is opposed to the blade by bending the tip portion of the processing device, and finally the rotary processing member is rotated.
There is a certain distance between each access port and the corresponding blade, and the distance depends on the location in an engine and the type of engine. Further, after the processing device is inserted into the engine, the rotary processing member needs to be brought into contact with the blade by curving the tip portion of the endoscope apparatus.
Conventionally, as disclosed in, for instance, U.S. Pat. Nos. 5,251,611 and 5,522,788, the curving structure of ordinary endoscopes is used in which to obtain a curve a curving portion is formed by connecting together a plurality of block members. However, in this case, because of a gap between the opposed faces of the curving blocks of the curving portion, the portion on the tip side of the curving portion easily wobbles due to reaction force of grinding, disabling stable operation. Further, since the curving portion has a certain curvature, the accessibility is poor when a blade close to the access port is to be ground. U.S. Pat. No. 5,522,788 has an additional problem that the length of the portion on the tip side of the curving location cannot be changed freely as occasion demands.
U.S. Pat. No. 4,790,624 proposes a prior art technique having a curving structure that can be curved at a very small radius of curvature. This is configured such that a bending portion having a given space is formed between a tip member and an insertion member and a bending member consisting of a plurality of shape-memory alloy elements is provided in the bending portion. Bending is effected by controlling the heating of the shape-memory alloy elements of the bending member.
However, U.S. Pat. No. 4,790,624 has problems that to obtain a curve it is necessary to continue heating the shape-memory alloy elements, and that a fine temperature control for the curve control is difficult.
In view of the above, the present assignee filed Japanese Patent Application No. Hei. 8-109586. FIGS. 1 and 2 show this apparatus.
This apparatus comprises a processing device main body 301, a rotary processing member 302 and an endoscope 303. The processing main body 301 is composed of an insertion portion 304 and a tip member 302. A bending portion 306 is formed between the insertion portion 304 and the tip member 305 so as to provide a given space in between. As shown in FIG. 2, having a hinge structure, the bending portion 306 is bent by means of a manipulation wire 309 that is pulled as a rotation adjustment knob 308 is rotated. The processing device main body 301 guides the rotary processing member 302 and the endoscope 303 to the tip member 305. To accommodate the fact that the distance between an access port and a blade varies case by case, adaptors 310 having a plurality of lengths are provided for the tip member 305 to change the distance between the bending portion 306 and the rotary processing means 302.
However, since the bending portion 306 has the hinge structure, the above configuration has a problem that the bending portion 306 does not have a sufficient spatial margin for accommodation of such internal components as the rotary processing device 302 and the endoscope 303. To secure a sufficient spatial margin, the diameter of the insertion portion 304 including the bending portion 306 necessarily increases. On the other hand, to decrease the diameter, because of the insufficient spatial margin, it is necessary to thin a rotary shaft for rotating the rotary processing member 302 or an image guide and a light guide in the endoscope 303. If the image guide is thinned, there occurs a problem that an image having a sufficient number of pixels cannot be obtained. If the light guide is thinned, there arises a problem that illumination of sufficient brightness cannot be obtained. If the rotary shaft is thinned, there occurs a problem of insufficient strength.
The adaptors 310 are attached and removed to change the distance between the bending portion 306 and the rotary processing member 302. However, this is associated with problems that the operation of attachment and detachment of the adaptors 310 is complex and that the preparation of a plurality of replacement adaptors 310 having different lengths is costly.